Method of making images on metal plates



C. J. STAUD METHOD OF MAKING IMAGES ON METAL PLATES Filed Aug. 27, 1942K l 1 GLASS PLATE 3 LAYERW/7'H :K' I I '41 SILVER/MAG? wvsm. HATESENSITIVE LAYER A T'TORNE YS Patented Aug. 14, 1945 METHOD OF MAKINGIMAGES N METAL PLATES Cyril J. Stand, Rochester, N. Y., assignor toEastman Kodak Company, Rochester, N. Y., a corporation of New JerseyApplication August 27, 1942, Serial No. 456,372

2 Claims.

This invention relates to a method of makin images on metal plates, moreparticularly useful as a step in the making of relief images in zincplates by a process involving etching through a relief image.

Ordinarily the plates are coated with a gelatin or albumen layersensitized with potassium dichromate and exposed under a negativecarried on clear glass or film, the exposure being prolonged because oflow sensitivity of the material.

It is well known that in making gelatin relief images on glass, it iscustomary and desirable that exposures be made through the support, thushardening the gelatin nearest to the support preliminary to washing offthe unaffected soft gelatin. This has not been possible with an opaquemetal plate, and it has accordingly been necessary that the exposure beprolonged to make certain that exposure at all points is complete. Thisrestricts the latitude of exposure and tends to obliterate detail.

I propose to overcome this difiiculty by utilizing X-rays to makeexposures through the zinc plate and through a metal image having agreater opacity to X-rays than the metal of the plate.

Reference is made to the diagrammatic figure of the accompanyingdrawing.

The metal plate I, usually of zinc, can be coated with an unhardened,photographic gelatino silver halide emulsion layer 2 in any suitableway. A most convenient method is by means of a transfer film from whichthe emulsion layer alone is stripped and transferred to the metal plate.Such a film and a method for transferring it are disclosed in the patentof Gale F. Nadeau, No. 2,326,048, of August 3, 1943, and the pendingapplication of Victor N. Gioseffi, Serial No. 452,928, filed July 30,1942.

Against the back or unsensitized surface of the zinc plate is placed aline negative or half-tone screen glass negative 3 bearing a layer 4containing a silver image. For the sake of clearness, plates I and 3 areshown as slightly spaced. This is then exposed to X-rays from tube 5which pass in succession through the negative or image, the zinc plateand the photographic emulsion. Because of the greater density to X-raysof silver than zinc, an image is formed in the sensitive layer. This isdeveloped in a tanning developer, of a well known type, and theunaffected and still unhardened gelatin washed off in warm water leavinga gelatin relief image. Other known means of obtaining the relief imagecould be used.

This process depends on the fact that absorption of X-rays by silver ismany times that of zinc. To maintain the difierential the zinc platewould be no thicker than practical requirements necessitate. The silverimage could be converted by known methods to uranium, platinum, or gold,which would ive even greater differential absorption than silver; andhence, greater contrast in the resultant image and, of course, othermetals, readily permeable to X-rays, could be used instead of zinc,where suitable for the process proposed.

Further control of contrast could be obtained by selection of suitablevoltages on the X-ray tube. In general, moderate voltages are mostsuitable.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The method of making a relief image on a metal plate that comprisescoating one surface of said plate with a sensitive layer, placing on theother side of the metal plate a layer transparent to X-rays carrying animage consisting of a metal more absorptive of X-rays than is the metalof the plate, passing X-rays through said image and the metal plate tothe sensitive layer and processing the sensitive layer to form a reliefimage therefrom.

2. The method of making a relief image oh a zinc plate that comprisescoating one surface thereof with an unhardened, sensitive,gelatinosilver halide layer, placing on the other side of the zinc platea support transparent to X-rays and carrying a silver photographicimage, passing X-rays through said image and said zinc plate to thesensitive layer to form a latent image therein, developing said latentimage in a developer that acts to tan the gelatin and washing oif theuntanned gelatin to form a relief image.

CYRIL J. STAUD.

